This invention relates to systems and methods for mapping catheter electrode position within a patient's body and, more particularly, a system and method which enables automatic real time three-dimensional measurement of catheter electrode position with an accuracy well less than 1 cm.
As is known, accurate position information is necessary for mapping, or localizing an accessory atrioventricular pathway. In this case, one can localize the ventricular or atrial insertion site of the pathway during antegrade or retrograde conduction through the pathway. The need for accurate positioning information is further illustrated by the standard method of cardiac mapping and subsequent ablation of the site of a ventricular tachycardia in a patient. The catheter is introduced into the atrium or ventricle, and the tip is positioned at an endocardial site. A tachycardia is induced, and the tip is moved to different positions, where the timing of sensed intracardiac signals is compared with ECG signals. Each position and the local activation moment must be accurately determined and recorded, so that an accurate map can be made from which the tachycardia focus can be determined. Following the mapping, the ablation tip must be accurately re-positioned with respect to the focus. This re-positioning places a great importance on being able to obtain accurate tip position information when and as the tip is moved to a position. Further, it is well known that frequently multiple ablations are often necessary in a relatively small area within the heart, in order to eliminate arrhythmogenic foci. Accordingly, the catheter is sequentially positioned at slightly different positions close to the focus, for producing lesions in the heart wall. These lesions are produced at different locations in order to ensure elimination of the foci. At present, it is difficult to obtain accurate and reliable information concerning the distances between successive ablation sites.
During hemodynamic and electrophysiologic cardiac catheterization procedures, cardiologists generally employ a monoplane and sometimes biplane fluoroscopic imaging to estimate the position of the catheter within the heart. However, with fluoroscopy, it is not yet possible to obtain automatic and objective three-dimensional information about the catheter position without laborious three-dimensional reconstruction from fluoroscopic images. As is readily understood, automatic measurement of the catheter position would be extremely useful during many interventional catheterization procedures.
Systems for obtaining three-dimensional catheter position data are known, but have serious limitations. For example, a magnetic system employs a special element in the catheter tip, the size and configuration of which make it useful for only certain catheter types. Given the many different types of catheters in use for different applications, a system and technique that would be able to accurately locate the position of any type catheter would constitute a significant advance.
The patent art contains a great many devices and systems directed toward catheter location. These systems embrace a number of different approaches, such as securing an inductor coil adjacent to the catheter tip with leads extending from the coil along the catheter for connection to external indicating equipment; positioning a varying magnetic field responsive component on the catheter or implement to be positioned, and using a movable external magnetic field source; use of a probe which generates a small magnetic field which is disturbed by a magnetically permeable metal in the device to be positioned; and the construction of various types of cardiac mapping probes and electrode configurations. However, these approaches have not proven commercially successful for one reason or another, and there remains a substantial need in the art for an improved technique of catheter mapping, particularly as applicable to cardiac catheterization and ablation procedures.